1. Field of the Invention
The present invention relates generally to an In-Phase/Quadrature Phase (I/Q) mismatch calibration method and apparatus, and more particularly, to a transceiver for use in any of Wireless Local Area Network (WLAN), Wireless Personal Area Network (PAN), and 3rd Generation (3G) and 4G cellular mobile communication systems.
2. Description of the Related Art
A mobile communication system can adopt Quadrature Modulation which uses orthogonal In-Phase (I) and Quadrature Phase (Q) simultaneously for up-conversion of a signal from baseband to passband and down-conversion from passband to baseband. The quadrature modulation is advantageous in terms of two-fold increase of transmission on a single carrier but disadvantageous in that a mismatch between the In-Phase and Quadrature Phase of the Local Oscillator (LO) causes mutual interference between I-phase and Q-phase signals and, thus, degrades system performance.
The I/Q mismatch may be divided into two categories, gain mismatch and phase mismatch. The gain mismatch denotes the difference in magnitude between I and Q components of the LO. The phase mismatch denotes the loss of the orthogonality in phase between I and Q components.
If the I/Q mismatch occurs at the quadrature modulator of a transceiver, this degrades Error Vector Magnitude (EVM) and increases Packet Error Rate (PER), resulting in degradation of entire system. Particularly, radio communication systems such as WLAN, WPAN, 3G and 4G cellular communication systems adopt high order modulation schemes including 16 Quadrature Amplitude Modulation (QAM), 64QAM, and 256QAM, which requires calibration of the transceiver I/Q due to the I/Q mismatch, i.e., the radio communication systems become more sensitive to the transceiver I/Q mismatch as the modulation order increases.